U.S. patent application Publication Ser. No. 2003/0024574 A1 to Tsen discloses a safety valve for steam cleaner. When steam is generated in the steam chamber by heating, the pressurized steam passes through the air inlet 112 of the valve body 11 and the center through hole 121 of the valve tube 12 into the air chamber 1621 of the actuating member 16 to expand the diaphragm 162 and to further force the push rod 163 upward, thereby causing the push rod 163 to lift the clutch member 17 upwardly away from the driving disk 15. After disengagement of the legs 172 of the clutch member 17 from the peripheral notches 151 of the driving disk 15, the rotary motion of the cap 18 does not drive the valve body 11 to rotate, i.e., removing the safety valve 1 is impossible. When inside pressure of the steam chamber 21 surpasses the spring power of the compression spring 124, the valve tube 12 is forced upwards from the air inlet 112 of the valve body 11 against the compression spring 124, enabling steam to pass through the air inlet 113 to outside of the steam cleaner 2, keeping inside pressure of the steam chamber 21 below the safety range. As a result, it is possible of preventing steam from rushing out of the steam cleaner 2 accidentally. Thus, continuing improvements in the exploitation of safety device for steam cleaner are constantly being sought.